US5723404A - Process for the production of mixed oxide powders for catalysts for the removal of nitrogen oxides - Google Patents
Process for the production of mixed oxide powders for catalysts for the removal of nitrogen oxides Download PDFInfo
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- US5723404A US5723404A US08/649,924 US64992496A US5723404A US 5723404 A US5723404 A US 5723404A US 64992496 A US64992496 A US 64992496A US 5723404 A US5723404 A US 5723404A
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- 238000000034 method Methods 0.000 title claims abstract description 52
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 title claims abstract description 51
- 230000008569 process Effects 0.000 title claims abstract description 51
- 239000003054 catalyst Substances 0.000 title claims abstract description 28
- 239000000843 powder Substances 0.000 title claims abstract description 20
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 12
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 69
- 239000000725 suspension Substances 0.000 claims abstract description 23
- IYVLHQRADFNKAU-UHFFFAOYSA-N oxygen(2-);titanium(4+);hydrate Chemical compound O.[O-2].[O-2].[Ti+4] IYVLHQRADFNKAU-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000001354 calcination Methods 0.000 claims abstract description 14
- 239000012065 filter cake Substances 0.000 claims abstract description 13
- 238000001914 filtration Methods 0.000 claims abstract description 10
- 239000000470 constituent Substances 0.000 claims abstract description 9
- 239000007787 solid Substances 0.000 claims abstract description 9
- 238000005406 washing Methods 0.000 claims abstract description 9
- 150000003839 salts Chemical class 0.000 claims abstract description 7
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 6
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 6
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052751 metal Inorganic materials 0.000 claims abstract description 5
- 239000002184 metal Substances 0.000 claims abstract description 5
- 239000001117 sulphuric acid Substances 0.000 claims abstract description 5
- 235000011149 sulphuric acid Nutrition 0.000 claims abstract description 5
- 238000001035 drying Methods 0.000 claims abstract 4
- 230000003472 neutralizing effect Effects 0.000 claims abstract 2
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 27
- 229910021653 sulphate ion Inorganic materials 0.000 claims description 22
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 150000003863 ammonium salts Chemical class 0.000 claims description 8
- 239000000047 product Substances 0.000 claims description 7
- 239000010936 titanium Substances 0.000 claims description 4
- 238000004061 bleaching Methods 0.000 claims description 3
- 239000003546 flue gas Substances 0.000 claims description 3
- 239000002994 raw material Substances 0.000 claims description 3
- 238000001694 spray drying Methods 0.000 claims description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 2
- 229910052719 titanium Inorganic materials 0.000 claims description 2
- 230000003197 catalytic effect Effects 0.000 claims 1
- 230000003301 hydrolyzing effect Effects 0.000 claims 1
- 229910000473 manganese(VI) oxide Inorganic materials 0.000 claims 1
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Chemical compound O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 abstract description 16
- 150000002739 metals Chemical class 0.000 abstract description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 27
- 239000000243 solution Substances 0.000 description 18
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 10
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 7
- 239000002253 acid Substances 0.000 description 7
- 229910021529 ammonia Inorganic materials 0.000 description 7
- 238000001556 precipitation Methods 0.000 description 7
- 235000011121 sodium hydroxide Nutrition 0.000 description 7
- 239000008367 deionised water Substances 0.000 description 6
- 229910021641 deionized water Inorganic materials 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- 238000006386 neutralization reaction Methods 0.000 description 6
- -1 for example clays Substances 0.000 description 5
- 239000002243 precursor Substances 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 230000007062 hydrolysis Effects 0.000 description 4
- 238000006460 hydrolysis reaction Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000002244 precipitate Substances 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 3
- 235000011114 ammonium hydroxide Nutrition 0.000 description 3
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 3
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 3
- 239000001166 ammonium sulphate Substances 0.000 description 3
- 235000011130 ammonium sulphate Nutrition 0.000 description 3
- 239000007795 chemical reaction product Substances 0.000 description 3
- XAYGUHUYDMLJJV-UHFFFAOYSA-Z decaazanium;dioxido(dioxo)tungsten;hydron;trioxotungsten Chemical compound [H+].[H+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O.[O-][W]([O-])(=O)=O XAYGUHUYDMLJJV-UHFFFAOYSA-Z 0.000 description 3
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 3
- LLZRNZOLAXHGLL-UHFFFAOYSA-J titanic acid Chemical compound O[Ti](O)(O)O LLZRNZOLAXHGLL-UHFFFAOYSA-J 0.000 description 3
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 3
- 229910003556 H2 SO4 Inorganic materials 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000001464 adherent effect Effects 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 235000019270 ammonium chloride Nutrition 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 238000010531 catalytic reduction reaction Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 150000004679 hydroxides Chemical class 0.000 description 2
- 239000013067 intermediate product Substances 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- 150000003608 titanium Chemical class 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- 239000010937 tungsten Substances 0.000 description 2
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 241000264877 Hippospongia communis Species 0.000 description 1
- 229910010415 TiO(OH) Inorganic materials 0.000 description 1
- 229910052770 Uranium Inorganic materials 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000001339 alkali metal compounds Chemical class 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 230000003113 alkalizing effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- QGAVSDVURUSLQK-UHFFFAOYSA-N ammonium heptamolybdate Chemical compound N.N.N.N.N.N.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.[Mo].[Mo].[Mo].[Mo].[Mo].[Mo].[Mo] QGAVSDVURUSLQK-UHFFFAOYSA-N 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- UNTBPXHCXVWYOI-UHFFFAOYSA-O azanium;oxido(dioxo)vanadium Chemical compound [NH4+].[O-][V](=O)=O UNTBPXHCXVWYOI-UHFFFAOYSA-O 0.000 description 1
- 229910001422 barium ion Inorganic materials 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000003311 flocculating effect Effects 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 239000012456 homogeneous solution Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000002574 poison Substances 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 238000000859 sublimation Methods 0.000 description 1
- 230000008022 sublimation Effects 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- HDUMBHAAKGUHAR-UHFFFAOYSA-J titanium(4+);disulfate Chemical compound [Ti+4].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O HDUMBHAAKGUHAR-UHFFFAOYSA-J 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 229910001930 tungsten oxide Inorganic materials 0.000 description 1
- LSGOVYNHVSXFFJ-UHFFFAOYSA-N vanadate(3-) Chemical class [O-][V]([O-])([O-])=O LSGOVYNHVSXFFJ-UHFFFAOYSA-N 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
- 238000004056 waste incineration Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 239000012463 white pigment Substances 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
- B01J21/063—Titanium; Oxides or hydroxides thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8628—Processes characterised by a specific catalyst
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0236—Drying, e.g. preparing a suspension, adding a soluble salt and drying
Definitions
- the present invention relates to a process for the production of mixed oxide powders for catalysts for the removal of nitrogen oxides from the flue gases (denox catalysts).
- catalysts suitable for the catalytic reduction consist of
- Catalysts like these that contain TiO 2 in the form of anatase as chief constituent and support and V 2 O 5 as well as MoO 3 and/or WO 3 as catalytically active minor constituents have gained special importance industrially. Catalysts like these are disclosed e.g. in EP-A 472 014, EP-A 385 164 and EP-A 317 875.
- the catalysts can in principle be produced by any process that ensures a sufficiently intimate mixing of the components:
- the components are homogeneously mixed in solution and pyrolyzed together or coprecipitated as hydroxides or carbonates, which are then ignited to give the oxides (homogeneous solution or coprecipitation process according to DE 2 458 888),
- one part of the components is used in precipitated form, and the other as solution and optionally precipitated, with subsequent calcination (simultaneous application of solution and precipitation processes according to DE 2 458 888),
- solid oxide precursors e.g. hydroxides
- pyrolysis precipitate mixing process according to DE 2 458 888
- the mixing of the ignited oxides by grinding together is less advantageous from the standpoints of energy consumption and the generation of noise and dust.
- those processes are in principle to be preferred in which at least one of the components is used in the liquid, e.g. dissolved, form. A combination of solution and precipitate processes is frequently employed.
- the mixed oxide powder obtained by one of the afore-mentioned processes is usually kneaded after the addition of water with suitable additive, for example clays, glass fibers, pore-formers and organic binders, and processed to shaped bodies, e.g. plates or honeycombs, and calcined.
- suitable additive for example clays, glass fibers, pore-formers and organic binders
- the catalysts can also be produced by first mixing only the TiO 2 precursor with a WO 3 or MoO 3 precursor and igniting to a TiO 2 /WO 3 or TiO 2 /MoO 3 mixed oxide powder, which is subsequently mixed with the V 2 O 5 precursor and processed as described above to catalysts for the removal of nitrogen oxides.
- aqueous titanium salt solutions e.g. titanium chloride or titanyl sulphate solutions
- an aqueous ammonia solution is used as the component with alkaline reaction for precipitation.
- orthotitanic acid is precipitated with aqueous ammonia solution from a titanium tetrachloride solution and after the addition of the oxides of molybdenum, tungsten and vanadium (or the corresponding precursors) and in some cases further components, processed to catalysts.
- JP 02/083 034 teaches that mixed oxide powders of TiO 2 and oxides of vanadium, tungsten or molybdenum at sulphate contents above 4.0% tend to undesirable particle aggregation and furthermore that the mechanical strength of the catalyst is reduced.
- a TiO 2 /WO 3 or TiO 2 /MoO 3 mixed oxide powder is produced by addition of ammonia to a Ti oxide hydrate slurry up to a pH value of 8.5, subsequent addition of ammonium paratungstate or paramolybdate followed by calcination.
- the purpose of the ammonia addition in this process is to reduce the sulphate content by converting the previously adsorbed sulphate into free ammonium sulphate, which sublimes off in the calcination step.
- ammonia has in principle the advantage that the ammonium salts formed as by-products during the precipitation and neutralization, e.g. according to
- xTiO(OH) 2 *yH 2 SO 4 means a titanium dioxide hydrate suspension with adherent sulphuric acid from the sulphate process
- the object is to provide a process that enables mixed oxide powders for catalysts for the removal of nitrogen oxides to be produced simply and at low cost, without the disadvantages of the previous processes.
- the present invention provides a process for the production of mixed oxide powders that contain as chief constituent TiO 2 in the form of anatase and as minor constituents one or more of the catalytically active oxides MOO 3 , WO 3 and V 2 O 5 , for catalysts for the removal of nitrogen oxides, that is characterized in that
- a titanium dioxide hydrate suspension containing sulphuric acid is partially neutralized with alkaline liquor to a pH value between 4.0 and 6.0 at temperatures between 20° and 100° C.
- sulphate-containing suspension of titanium dioxide hydrate e.g. orthotitanic acid or metatitanic acid
- the particularly preferred starting material is purified, so-called bleached TiO 2 hydrolyzate from the sulphate process, as described in Ullmann's Encyclopedia of Industrial Chemistry, 4th Edition, Volume 18, page 576.
- the cake obtained by digestion is dissolved in cold water or in dilute acid recycled from the process.
- titanium oxide hydrate is precipitated by hydrolysis at 94°-110° C.
- Other sulfuric-acid-soluble components of the raw material are precipitated simultaneously, mainly niobium as its oxide hydrate.
- Hydrolysis is carried out in brick-lined, stirred tanks into which steam is passed.
- the liquid phase of the titanium oxide hydrate suspension contains 20-28% H 2 SO 4 and various amounts of dissolved sulfates, depending on the raw material.
- the hydrate is filtered off from the solution and washed with water or dilute acid. Even with acid washing, too many heavy metal ions are adsorbed on the hydrate for it to be directly usable in the production of white pigment.
- Most of the impurities can be removed by reduction (bleaching), whereby the filter cake is slurried with dilute acid (3-10%) at 50°-90° C. and mixed with zinc or aluminum powder. Bleaching can also be carried out with powerful nonmetallic reducing agents (e.g., HOCH 2 -SO 2 Na).
- Such hydrolyzate suspensions preferably contain 20 to 40 wt % solid.
- the hydrolyzate is partially neutralized with an alkaline liquor, caustic soda solution preferably being used for economic reasons. It is particularly advantageous to carry out the neutralization with intensive mixing and measurement of the pH value.
- the essential feature of the first process step is that the partial neutralization is carried out to a pH value in the weakly acid range, i.e. between 4.0 and 6.0.
- a pH value in the weakly acid range i.e. between 4.0 and 6.0.
- hydrous MOO 3 , WO 3 or V 2 O 5 during the addition in a later step-of soluble molybdates, tungstates or vanadates, whereby the homogeneity of the product suffers.
- alkali cations e.g.
- the temperature can be between 20° C. and 100° C.; particularly, however, the operation is carried out between about 30° C. and 60° C.
- the filtration and careful washing of the partially neutralized hydrolyzate follows.
- any device can be used for this purpose that permits a very intensive washing of fine precipitates.
- suitable processes and apparatuses are known to the expert, for example, filtration via a filter press or via a rotary vacuum filter, Moore filtration and cross-current filtration.
- the partially neutralized, filtered and washed hydrolyzate is subsequently suspended in deionized water and the desired amount of MoO 3 , WO 3 or V 2 O 5 is added in the form of suitable water-soluble salts and the mixture well mixed.
- suitable water-soluble salts Preferably ammonium salts of the corresponding mono- or isopolyanions are used, e.g. ammonium heptamolybdate, ammonium para- or metatungstate and ammonium metavanadate. Both solid salts and solutions can be used.
- the suspension so treated is then dried, e.g. by spray drying, and the dried material calcined, for example in a rotary furnace.
- the dried material calcined, for example in a rotary furnace.
- the mixed oxide powders can be processed in well known way to catalysts for the removal of nitrogen oxides.
- the TiO 2 hydrate was then filtered off in portions via polyester filter cloth familiar to the expert, and thoroughly washed with hot deionized water at 80° C.
- the collected filter cakes were mixed with deionized water to a suspension with a TiO 2 content of 20 wt.-%.
- Example 1 aqueous ammonia solution was added to 2400 g of this suspension, corresponding to 720 g TiO 2 , to adjust the pH value to 8.5 (at RT, about 30° C.). For this purpose, 111.4 g of a concentrated aqueous NH 3 solution (30 wt %) were used. After the addition of 90.0 g solid ammonium paratungstate (89.1 wt % WO 3 ) and kneading for one hour, the mixture was concentrated on a rotary evaporator at a maximum bath temperature of 60° C. and dried at 130° C.
- 90.0 g solid ammonium paratungstate 89.1 wt % WO 3
- the analytical data show that it is possible by the process according to the invention to obtain a mixed oxide powder corresponding to the prior art and suitable for the production of catalysts for the removal of nitrogen oxides.
- the content of harmful sodium by the process according to the invention is about as low, and thus about as favorable, as that by the prior art.
- the sulphate content is below 4%, as required by JP 02/083034.
- the specific surface areas of the two powders are comparable.
- the advantage of the process according to the invention becomes evident in the specific NH 3 emission during the calcination; in the example of the present invention, the concentration of ecologically undesirable NH 3 or corrosive ammonium salts in the waste gas and waste water of the calcination furnace is reduced by not less than 75%.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Environmental & Geological Engineering (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Biomedical Technology (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- General Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Catalysts (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
Description
4NO+4NH.sub.3 +O.sub.2 →4N.sub.2 +6H.sub.2 O
TiCl.sub.4 +4NH.sub.3 +3H.sub.2 O→TiO(OH).sub.2 +4NH.sub.4 Cl
xTiO(OH).sub.2 *yH.sub.2 SO.sub.4 +2yNH.sub.3 →xTiO(OH).sub.2 +y(NH.sub.4).sub.2 SO.sub.4
TABLE ______________________________________ Analytical Data of the TiO.sub.2 /WO.sub.3 powder Example Comparison ______________________________________ Na.sub.2 O ppm! 20 22 SO.sub.4.sup.2- %! 2.66 2.75 BET m.sup.2 /g! 87 81 specific NH.sub.3 emission 6.0 24.3 g NH.sub.3 /kg end product! ______________________________________
Claims (10)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/649,924 US5723404A (en) | 1993-06-29 | 1996-05-16 | Process for the production of mixed oxide powders for catalysts for the removal of nitrogen oxides |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE4321555.6 | 1993-06-29 | ||
DE4321555A DE4321555C1 (en) | 1993-06-29 | 1993-06-29 | Process for producing mixed-oxide powders for denitration catalysts |
US26398094A | 1994-06-22 | 1994-06-22 | |
US08/649,924 US5723404A (en) | 1993-06-29 | 1996-05-16 | Process for the production of mixed oxide powders for catalysts for the removal of nitrogen oxides |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US26398094A Continuation | 1993-06-29 | 1994-06-22 |
Publications (1)
Publication Number | Publication Date |
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US5723404A true US5723404A (en) | 1998-03-03 |
Family
ID=6491479
Family Applications (1)
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US08/649,924 Expired - Fee Related US5723404A (en) | 1993-06-29 | 1996-05-16 | Process for the production of mixed oxide powders for catalysts for the removal of nitrogen oxides |
Country Status (8)
Country | Link |
---|---|
US (1) | US5723404A (en) |
EP (1) | EP0640386B1 (en) |
JP (1) | JP3694537B2 (en) |
CA (1) | CA2126718A1 (en) |
DE (2) | DE4321555C1 (en) |
ES (1) | ES2094012T3 (en) |
FI (1) | FI115507B (en) |
NO (1) | NO302339B1 (en) |
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CN112408470A (en) * | 2020-10-30 | 2021-02-26 | 甘肃盈华环保科技有限公司 | Method for producing titanium dioxide by using waste denitration catalyst based on high-temperature calcination method |
CN112221485A (en) * | 2020-11-13 | 2021-01-15 | 重庆新华化工有限公司 | Preparation method of Ti-Mo or Ti-Mo-V catalyst titanium dioxide for reducing burning loss |
Also Published As
Publication number | Publication date |
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DE59400939D1 (en) | 1996-12-05 |
JPH0796185A (en) | 1995-04-11 |
FI943080A (en) | 1994-12-30 |
FI943080A0 (en) | 1994-06-27 |
NO942444L (en) | 1994-12-30 |
JP3694537B2 (en) | 2005-09-14 |
EP0640386B1 (en) | 1996-10-30 |
EP0640386A1 (en) | 1995-03-01 |
DE4321555C1 (en) | 1994-09-15 |
CA2126718A1 (en) | 1994-12-30 |
NO942444D0 (en) | 1994-06-28 |
NO302339B1 (en) | 1998-02-23 |
FI115507B (en) | 2005-05-31 |
ES2094012T3 (en) | 1997-01-01 |
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